Actinic radiation-reactive pressure-sensitive adhesive composition

ABSTRACT

An actinic radiation-reactive pressure-sensitive adhesive composition which can be cured in air at a high speed, without irritation and bad smell, comprises 
     1 a pressure-sensitive adhesive compound comprising an acrylate copolymer and 
     2 an actinic radiation-curable resin comprising (1) one or more polythiol compounds and (2) one or more polyene compounds each having an least two actinic radiation-reactive acrylate carbon-to-carbon double bonds in the molecule.

This is a continuation of Ser. No. 07/632 190, filed Dec. 21, 1990 nowU.S. Pat. No. 5,278,199 issued Jan. 11, 1994.

FIELD OF INDUSTRIAL APPLICATION

The present invention relates to a reactive pressure-sensitive adhesivecomposition. More particularly, it relates to an actinicradiation-reactive pressure-sensitive adhesive composition, thepressure-sensitive adhesiveness of which is lost or reduced byirradiation with an actinic radiation such as ultraviolet rays.

PRIOR ART

A semiconductor wafer of silicon or gallium arsenide is cut into chipshaving predetermined sizes in a dicing step and transferred to amounting seem through several steps such as expanding. In this dicingstep, a semiconductor wafer is cut in a state in which it is fixed on apressure-sensitive adhesive sheet comprising a film of a plastic such aspolyethylene, polypropylene or crosslinked polyolefin and apressure-sensitive adhesive layer formed thereon, and in the mountingstep, the chips are picked up, i.e., peeled off the sheet, and mounted.The pressure-sensitive adhesive to be used in the preparation of theabove sheet is required to satisfy the requirements that a semiconductorwafer neither shifts nor is released in a dicing step and that the chipsbe easily picked up without leaving the adhesive thereon. Although asynthetic resin base pressure-sensitive adhesive comprising an acrylicor polyester synthetic resin and a crosslinking agent and a rubber basepressure-sensitive adhesive comprising a natural or synthetic rubber anda tackifier have been used as the pressure-sensitive adhesive for thepressure-sensitive adhesive sheet in the dicing step of a semiconductorwafer, these adhesives did not satisfy the above requirements.Therefore, there have been attempts to modify the pressure-sensitiveadhesive tape itself, e.g. to impart a well-balanced pressure-sensitiveadhesive force to the tape by applying a pressure-sensitive adhesive toonly a limited area of the tape, or to facilitate the pickup of a dicedsemiconductor wafer by washing it in a state in which it is adhered tothe tape with an organic solvent in the mounting step to lower theadhesive force.

However, modification of the tape has a detect that the obtained tapeexhibits problematic performances such as poor adhesive force in thedicing step and is problematic in respect of the preparation process ofthe tape and the cost thereof, while the lowering of the adhesive forceby the washing with an organic solvent necessitates the use of a lot ofa chlorinated solvent such as trichloroethylene, which constitutes asocial problem such as atmospheric pollution.

Recently, a process characterized by using a reactive pressure-sensitiveadhesive containing a thermosetting or actinic radiation-curable resinand curing the resin by heating or irradiation with an actinic radiationafter dicing to lower the pressure-sensitive adhesive force, therebyfacilitating its pickup in the mounting step, has been noticed as meansfor solving the above problems.

Such a reactive pressure-sensitive adhesive has an advantage that itexhibits a low adhesive force in the mounting step, though it exhibits asufficient adhesive force in the dicing step, which is a desirableperformance for the adhesive to be used in the dicing of a semiconductorwafer, and another advantage in that no problem such as atmosphericpollution is caused because no organic solvent is used in the process.

More particularly, the reactive pressure-sensitive adhesive to bepreferably used in the dicing of a semiconductor wafer is required toexhibit an adhesive force (90° peel strength at a peel rate of 50mm/min) of 200 to 1000 g/20 mm for a semiconductor wafer beforeirradiation with an actinic radiation such as ultraviolet rays and thatof 100 g/20 mm or below after curing. However, the performance of such areactive pressure-sensitive adhesive widely varies depending upon thereactivity of the curable resin used.

When the reactive pressure-sensitive adhesive is heated or irradiatedwith an actinic radiation such as ultraviolet rays, the curable resincontained in the adhesive will fully react to attain a higher molecularweight, so that adhesiveness of the adhesive itself is lowered andreleasability is imparted to the adhesive by virtue of the cureshrinkage caused therein, which brings about a lowering in the adhesiveforce thereof. However, when a curable resin having a low reactivity isused, the resin will not fully react, and thus fail in attaining ahigher molecular weight and gives too small a cure shrinkage to satisfythe above requirements. Further, it is necessary from the standpoint ofworkability that the adhesive be cured to lose or lower its adhesiveforce for a time as short as possible.

For these reasons, the use of an actinic radiation-curable resin issuperior to that of a thermosetting resin for preparing a reactivepressure-sensitive adhesive having excellent performance.

Examples of the actinic radiation-curable resin which is usable as thecurable resin for a reactive pressure-sensitive adhesive includeacrylate resins such as polyester acrylate, urethane acrylate, epoxyacrylate and polyether acrylate resins; unsaturatec polyester resins,epoxy resins, and polyene-thiol resins. With respect to the adhesivecontaining an acrylate resin, for example, there have been proposed anadhesive containing a polyester acrylate as the actinicradiation-curable resin which is suitable for the pressure-sensitiveadhesive sheet disclosed in Japanese Patent Laid-Open Nos. 196956/1985and 223139/1985 and an adhesive containing a urethane acrylate resin asthe actinic radiation-curable resin which is suitable for thepressure-sensitive adhesive sheen disclosed in Japanese Patent Laid-OpenNos. 205179/1987 and 205180/1987. However, these adhesives characterizedby containing an acrylate resin as the actinic radiation-curable resincannot exhibit sufficient performance in air because the cure thereof isinhibited by oxygen, so that the dicing of a semiconductor wafer must beconducted in, for example, an inert gas such as nitrogen or a vacuum.Under these circumstances, the development of an actinicradiation-reactive pressure-sensitive adhesive composition which can becured at a high rate, even in air without suffering from cure inhibitionby oxygen has been sought.

Further, when a polyfunctional monomer or diluent is added to anacrylate resin to improve the reactivity of the resin in the air, theresulting composition has another problem of being highly irritating tothe skin and very smelly.

SUMMARY OF THE INVENTION

The inventors of the present invention have studied to obtain an actinicradiation-reactive pressure-sensitive adhesive composition which cansatisfy the various characteristics necessary for the pressure-sensitiveadhesive to be used in a pressure-sensitive adhesive sheet for fixing asemiconductor wafer in the dicing thereof and have found that an actinicradiation-reactive pressure-sensitive adhesive composition which can becured at a high rate, even in air, without suffering from cureinhibition by oxygen, exhibits an adhesive force (90° peel strength at apeel rate: 50 mm/min) of 200 to 1000 g/20 mm for a semiconductor waferbefore curing and that of 100 g/20 mm or below after curing and has lowirritation to the skin can be obtained by using an actinicradiation-curable resin comprising one or more potythiol compounds andone or more polyene compounds having at least two actinicradiation-reactive carbon-to-carbon double bonds in the molecule. Thepresent invention has been accomplished on the basis of this finding.

The actinic radiation-reactive pressure-sensitive adhesive compositionof the present invention is characterized by comprising as the essentialcomponents:

1 a pressure-sensitive adhesive organic compound, and

2 an actinic radiation-curable resin comprising (1) one or morepolythiol compounds and (2) one or more polyene compounds each having atleast two actinic radiation-reactive carbon-to-carbon double bonds inthe molecule.

The pressure-sensitive adhesive organic compound to be used as aconstituent in the present invention may be any conventional one andexamples thereof include natural rubber, isoprene rubber,styrene-butadiene rubber, styrene-butadiene block copolymer, butylrubber, polyisobutylene, silicone rubber, polyvinyl isobutyl ether,chloroprene rubber, nitrile rubber, graft rubber, reclaimed rubber,saturated copolyester resin, acrylate polymer, and acrylate copolymer,among which saturated copolyester resin and acrylate copolymer areparticularly preferable.

The saturated copolyester resin is one prepared by the esterification ofone or more saturated polycarboxylic acids with one or more saturatedpolyhydric alcohols and having a relatively low glass transitiontemperature. Examples of the saturated polycarboxylic acid includeterephthalic, isophthalmic, phthalic, 2,6-naphthalenedicarboxylic,diphenyldicarboxylic, succinic, adipic, azelaic, sebacic, dodecanedionicand 1,4-cyclohexanedicarboxylic acids and trimellitic anhydride.Examples of the saturated polyhydric alcohol include ethylene glycol,diethylene glycol, triethylene glycol, polyethylene glycol, propyleneglycol, dipropylene glycol, polypropylene glycol, 1,3-butanediol,1,4-butanediol, 1,6-hexanediol, neopentyl glycol, bisphenol A,hydrogenated bisphenol A, bisphenol A-ethylene oxide adduct, bisphenolA-propylene oxide adduct, thiodiethanol, trimethylolpropane, glycerol,triethanolamine, pentaerythritol, dipentaerythritol, sorbitol,hydroquinone, pyrogallol, xylylene glycol,4,4'-dihydroxydiphenylmethane, trishydroxyethyi isocyanurate andbishydroxyethylhydantoin ethylene glycol and adducts thereof withalkylene oxide such as ethylene oxide or propylene oxide. Among thesaturated copolyester resins described above, saturated copolyesterresins prepared by the esterification of one or more saturateddicarboxylic acids with one or more saturated dihydric alconois arepreferable. Particularly, a saturated copolyester resin prepared by theesterification of saturated dicarboxylic acids with saturated dihydricalcohols at a molar ratio between 80:20 and 20:80 is still preferablyused as the pressure-sensitive adhesive organic compound constitutingthe actinic radiation-reactive pressure-sensitive adhesive compositionaccording to the present invention.

The saturated copolyester resin to be used in the present invention maycontain a crosslinking agent to control the adhesive force of theadhesive composition and examples of the crosslinking agent includemelamine, isocyanate, acid anhydride, amine, epoxy resin and phenolicresin.

The acrylate copolymer to be used in the present invention is an acrylicresin prepared by the addition polymerization of two or more acrylicmonomers and particularly, an acrylic resin comprising a soft mainmonomer having a low glass transition point for impartingpressure-sensitive adhesiveness to the copolymer, a hard comonomerhaving a high glass transition point in a low content for impartingadhesiveness and cohesive force to the copolymer and a functionalmonomer for improving the crosslinkability and adhesiveness of thecopolymer is preferable. Preferred examples of the main monomer of theacrylate copolymer include ethyl acrylate, butyl acrylate and2-ethylhexyl acrylate, those of the comonomer include vinyl acetate,acrylonitrile, acrylamide, styrene, methyl methacrylate, and methylacrylate; and those of the functional monomer include methacrylic,acrylic and itaconic acids; hydroxyethyl methacrylate, hydroxypropylmethacrylate, dimethylaminoethyl methacrylate, methylolacrylamide,glycidyl methacrylate and maleic anhydride. Among the acrylatecopolymers described above, an acrylate copolymer having a weight ratioof the main monomer to the comonomer of between 90:10 and 10:90 andcontaining a functional monomer in an amount of 0.1 to 10 parts byweight per 100 parts by weight of the sum total of the main monomer andthe comonomer is particularly preferably used as the adhesive organiccompound constituting the actinic radiation-reactive pressure-sensitiveadhesive composition of the present invention.

The acrylate copolymer may contain a crosslinking agent to control thepressure-sensitive adhesive force and examples thereof include melamine,isocyanate, acid anhydride, amine, epoxy resin and phenolic resin.

The actinic radiation-curable resin to be used as the other constituentin the present invention comprises one or more polythiol compounds andone or more polyene compounds, each having at least two actinicradiation-reactive carbon-to-carbon double bonds in the molecule.

The polythiol compound to be used as a constituent of the actinicradiation-curable resin according to the present invention is onerepresented by the general formula (1):

    A--(SH)q                                                   (1)

wherein A is an organic residue having a valence of q and no unsaturatedbond reactive with a SH group, and q is an integer of 2 or above,

having a molecular weight of 80 to 10000 and exhibiting a viscosity ofnearly 0 to 10000 P at 50° C. Preferred examples of the polythiolcompound include polythiols prepared by the esterification of apolyhydric alcohol with thioglycolic, α-mercaptopropionic orβ-mercaptopropionic acid; aliphatic or aromatic polythiols such asethanedithiol, propanedithiol, hexamethylenedithiol and xylylenedithiol;polythiols prepared by replacing the halogen atoms of an adduct of analcohol with epihalohydrin by mercapto groups; and reaction productsbetween polyepoxy compounds and hydrogen sulfide. Examples of thepolyhydric alcohol to be used in the above esterification ofthioglycolic or mercaptopropionic acid include ethylene glycol,diethylene glycol, triethylene glycol, polyethylene glycol, propyleneglycol, dipropylene glycol, polypropylene glycol, 1,3-butanediol,1,4-butanediol, 1,6-hexanediol, neopentyl glycol, bisphenol A,hydrogenated bisphenol A, bisphenol A-ethylene oxide adduct, bisphenolA-propylene oxide adduct, thiodiethanol, trimethylolpropane, glycerol,triethanolamine, pentaerythritol, dipentaerythritol, sorbitol,hydroquinone, pyrogallol, xylylene glycol,4,4'-dihydroxydiphenylmethane, trishydroxyethyl isocyanurate andbishydroxyethylhydantoin.

These polythiol compounds may be used alone or as a mixture of two ormore of them.

The polyene compound to be used as the other constituent of the actinicradiation-curable resin is preferably an organic compound having actinicradiation-reactive carbon-to-carbon double bonds in the molecule andexamples thereof include polybutadiene, polyisoprene, alkyl ether resin,allyl ester resin, allyl urethane resin, acrylate resin, methacrylateresin, vinyl ether resin, vinyl thioether resin, N-vinyl compound,unsaturated polyester resin, and vinylcycloacetal resin. Particularly,polyene compounds each having at least two actinic radiation-reactivecarbon-to-carbon double bonds in the molecule and derived from asubstituted or unsubstituted allyl alcohol, triallyl cyanurate andtriallyl isocyanurate are still preferably used as the polyene compoundconstituting the actinic radiation-curable resin according to thepresent invention.

The polyene compound having at least two actinic radiation-reactivecarbon-to-carbon double bonds in the molecule and derived from asubstituted or unsubstituted allyl alcohol is preferably a polyenecompound derived from an adduct of a substituted or unsubstituted allylalcohol with an epoxy-containing organic compound, and represented byone of the following general formulas (2) to (5): ##STR1## wherein R isa hydrogen atom or a group selected from among a phenyl group and alkylgroups each having 1 to 10 carbon atoms, wherein a plurality of R groupsmay be the same or different from each other; and Y is a groupcomprising units formed by the ring opening of one or more epoxycompounds selected from the group consisting of ethylene oxide,propylene oxide, butylene oxide, styrene oxide, cyclohexene oxide,epihalohydrin and allyl glycidyl ether through the cleavage of thecarbon-to-oxygen bond, which are arranged alone, in block or at random,with the proviso that at least one unit formed by the ring opening ofallyl glycidyl ether through the cleavage of the carbon-to-oxygen bondof the epoxy group is contained in Y, ##STR2## wherein R is a hydrogenatom or a group selected from among a phenyl group and alkyl groups eachhaving 1 to 10 carbon atoms, wherein a plurality of R groups may be thesame or different from each other; and Y is a group comprising unitsformed by the ring opening of one or more epoxy compounds selected fromthe group consisting of ethylene oxide, propylene oxide, butylene oxide,styrene oxide, cyclohexene oxide, epihalohydrin and allyl glycidyl etherthrough the cleavage of the carbon-to-oxygen bond, which are arrangedalone, in block or at random; Z is a group selected from the groupconsisting of residues of isocyanate-terminated monomers each having 1or 2 aromatic nuclei and a valence of (m+n), residues ofisocyanate-terminated monomers each having 1 or 2 alicyclic nuclei and avalence of (m+n), residues of isocyanate-terminated aliphatic monomerseach having a valence of (m+n), trimers of the isocyanate-terminatedmonomers described above, residues of isocyanate-terminated prepolymersprepared from hydroxyl-terminated saturated polyester polyol and theisocyanate-terminated monomer described above, residues ofisocyanate-terminated prepolymers prepared from hydroxyl-terminatedsaturated polyether polyol and the isocyanate-terminated monomersdescribed above and residues of isocyanate-terminated compounds preparedfrom the isocyanate-terminated monomers described above and polyhydricalcohols; k is an integer of 1 to 10, m is an integer of 1 to 6, and nis an integer of 0 to 5, with the proviso that the sum total of m and nis an integer of 2 or above, ##STR3## wherein R is a hydrogen atom or agroup selected from among a phenyl group and alkyl groups each having 1to 10 carbon atoms, wherein a plurality of R groups may be the same ordifferent from each other; and Y is a group comprising units formed bythe ring opening of one or more epoxy compounds selected from the groupconsisting of ethylene oxide, propylene oxide, butylene oxide, styreneoxide, cyclohexene oxide, epihalohydrin and allyl glycidyl ether throughthe cleavage of the carbon-to-oxygen bond, which are arranged alone, inblock or at random; B is a group selected from the group consisting ofresidues of saturated or unsaturated aliphatic carboxylic acids eachhaving 4 to 10 carbon atoms and a valence of (m+n) which are bonded toother groups through ester linkages, residues of carboxylic acids eachhaving one aromatic nucleus and a valance of (m+n) which are bonded toother groups through ester linkages, and residues of carboxylic acidseach having one alicyclic nucleus and a valence of (m+n) which arebonded to other groups through ester linkages; k is an integer of 1 to10, m is an integer of 1 to 6, and n is an integer of 0 to 5, with theproviso that the sum total of (m+n) is an integer of 2 or above,##STR4## wherein R' is a hydrogen atom, an l-valent organic residuehaving 1 to 30 carbon atoms and not containing any olefinic double bond,which may contain an oxygen, nitrogen, sulfur, silicon or halogen atomor a residue prepared by removing hydroxyl groups from a saturatedpolyester polyol having a molecular weight of 100 to 10000; Y is a groupcomprising units formed by the ring opening of one or more epoxycompounds selected from the group consisting of ethylene oxide,propylene oxide, butylene oxide, styrene oxide, cyclohexene oxide,epihalohydrin, and allyl glycidyl ether through the cleavage of thecarbon-to-oxygen bond, which are arranged alone, in block or at random,with the proviso that at least two units formed by the ring opening ofallyl glycidyl ether through the cleavage of the carbon-to-oxygen bondof the epoxy group are present; and Z is an integer of 1 to 6.

The polyene compound represented by the above general formula (2) isprepared by the addition of an epoxy-containing organic compound(containing at least one allyl glycidyl ether molecule) to a substitutedor unsubstituted allyl alcohol.

The addition of an epoxy-containing compound to a substituted orunsubstituted allyl alcohol can be conducted by various known processes.For examples, it can be easily conducted by incorporating a catalyst(such as BF₃ -ether complex) in an allyl alcohol and dropping allylglycidyl ether into the obtained mixture at an elevated temperature(about 60° C.) to complete a reaction.

Examples of the substituted or unsubstituted allyl alcohol to be used inthe above addition include allyl alcohol, crotyl alcohol,1-hydroxypentene-2, 1-hydroxyhexene-2, 1-hydroxyheptene-2,1-hydroxynonene-2, 1-hydroxydecene-2, 3-hydroxybutene-1,3-hydroxypentene-2, 2-hydroxyhexene-3, 3-hydroxy-2,3-dimethylbutene-1,4-hydroxy-2,3,4-trimethylpentene-2, and2-hydroxy-2,3,4,5-tetramethylhexene-3.

The epoxy-containing organic compound to be used in the above additionincludes ethylene oxide, propylene oxide, butylene oxide, allyl glycidylether, cyclohexene oxide, styrene oxide, and epihalohydrin. Theseepoxy-containing organic compounds may be added alone or two or more ofthem may be added at random or in block, with the proviso that at leastone allyl glycidyl ether unit is present in the obtained adduct.

Examples of the polyene compound represented by the general formula (2)include adducts of allyl alcohols with allyl glycidyl ether, adducts ofallyl alcohols with allyl glycidyl ether and epichlorohydrin, adducts ofallyl alcohols with allyl glycidyl ether and ethylene oxide, and adductsof allyl alcohols with allyl glycidyl ether, epichlorohydrin andethylene oxide.

The viscosity of the polyene compound represented by the general formula(2) at 50° C. is generally nearly 0 to 10000 P, preferably 1 to 1000 P.

The polyene compound represented by the above general formula (3) can beprepared by adding an epoxy-containing organic compound to a substitutedor unsubstituted allyl alcohol and reacting the obtained adduct with apolyisocyanate compound.

The addition of an epoxy-containing compound to a substituted orunsubstituted allyl alcohol can be conducted by various known processes.For examples, it can be easily conducted by incorporating a catalyst(such as BF₃ ether complex) in an allyl alcohol and dropping allylglycidyl ether into the obtained mixture at an elevated temperature(about 60° C.) to complete the reaction. Alternatively, some of suchadducts are commercially available (for example, an adduct of allylalcohol with 1 to 4 ethylene oxide units is commercially available underthe trade name of "Allyl glycol" (a product of Nippon Nyukazai Co.,Ltd.).

Examples of the substituted or unsubstituted allyl alcohol to be used inthe above addition include allyl alcohol, crotyl alcohol,1-hydroxypentene-2, 1-hydroxyhexene-2, 1-hydroxyheptene-2,1-hydroxynonene-2, 1-hydroxydecene-2, 3-hydroxybutene-1,3-hydroxypentene-2, 2-hydroxyhexene-3, 3-hydroxy-2,3-dimethylbutene-1,4-hydroxy-2,3,4-trimethylpentene-2, and2-hydroxy-2,3,4,5-tetramethylhexene-3.

The epoxy-containing organic compound to be used in the above additionincludes ethylene oxide, propylene oxide, butylene oxide, allyl glycidylether, cyclohexene oxide, styrene oxide and epihalohydrin. Theseepoxy-containing organic compounds may be added alone or two or more ofthem may be added at random or in block. Preferable examples of theadduct include adducts of allyl alcohols with allyl glycidyl ether,adducts of allyl alcohols with allyl glycidyl ether and epichlorohydrin,adducts of allyl alcohols with allyl glycidyl ether and ethylene oxide,and adducts of allyl alcohols with allyl glycidyl ether, epichlorohydrinand ethylene oxide.

A preferred polyene compound represented by the above general formula(3) can be prepared by reacting the adduct of a substituted orunsubstituted allyl alcohol with an epoxy-containing organic compoundthus prepared with a polyisocyanate compound. To illustrate thepreparation of the polyene compound more particularly, the polyenecompound can be prepared by feeding a commercially available adduct ofallyl alcohol with ethylene oxide (Allyl glycol, a product of NipponNyukazai Co., Ltd.) and Hylene W (dicyclohexylmethane 4,4'-diisocyanate;a product of Du Pont) in such amounts that the equivalent of thehydroxyl group is equal to that of the isocyanate group and carrying outa reaction according to a conventional process for the preparation of aurethane.

The polyisocyanate compound include not only Hylene W but also monomericpolyisocyanates such as tolylene diisocyanate, diphenylmethane4,4'-diisocyanate, xylylene diisocyanate, isophorone diisocyanate andhexamethylene diisocyanate; trimers of tolylene diisocyanate orisophorone diisocyanate; isocyanate-terminated prepolymers prepared fromhydroxy-terminated compounds such as saturated polyester polyol orpolyether polyol and the above monomeric polyisocyanate compounds; andisocyanate-terminated compounds prepared from the above monomericpolyisocyanate compounds and the polyhydric alcohols mentioned abovewith respect to the polythiol compound (1). The above polyester polyolcan be prepared by the esterification of a polyhydric alcohol asdescribed above with a polycarboxylic acid such as succinic, adipic,sebacic, phthalic, hexahydrophthalic, trimellitic or pyromellitic acid.The polyether polyol includes polyethylene glycol, polypropylene glycol,polybutylene glycol, polytetramethylene glycol, and adducts of the abovepolyhydric alcohols with alkylene oxides, which have each a molecularweight of 100 to 10000.

The polyene compound represented by the general formula (3) alsoincludes those prepared by the following process. Namely, an adduct of asubstituted or unsubstituted allyl alcohol,with an epoxy-containingcompound is reacted with a polyisocyanate compound in such a way thatpart of the isocyanate groups remain in an unreacted state and theremaining isocyanate groups are then reacted with an unsaturatedalcohol, with the proviso that this sequence of reaction is conducted insuch a way that at least one unit of the above adduct is contained ineach molecule. To illustrate the process more particularly, Allylglycol, which has been described above, is reacted with Hyiene W at anequivalent ratio of between 1.0:2.0 and 1.9:2.0 (in a state wherein theisocyanate group is excessive) to give a partially capped isocyanate.Then, the remaining isocyanate groups are reacted with allyl alcohol togive an objective polyene compound. Examples of the unsaturated alcoholinclude not only allyl alcohol but also crotyl alcohol,3-hydroxybutene-1, 4-hydroxy-pentene-2, 2-hydroxyhexene-3,2-hydroxyheptene-3, 2-hydroxyoctene-3, 2,3-dimethyl-l-hydroxybutene-2,2,3-dimethyl-3-hydroxypentene-2, 4-hydroxybutene-1, 5-hydroxypentene-1,6-hydroxyhexene-1, 7-hydroxy-heptene-1 and 8-hydroxyoctene-1.

The viscosity of the polyene compound represented by the general formula(3) at 50° C. is generally nearly 0 to 10000 P, preferably 1 to 1000 P.

The polyene compound represented by the above general formula (4) isprepared by adding an epoxy-containing organic compound to a substitutedor unsubstituted allyl alcohol and reacting the obtained adduct with anacid anhydride or a polybasic acid.

The addition of an epoxy-containing compound to a substituted orunsubstituted allyl alcohol can be conducted by various known processes.For examples, it can be easily conducted by incorporating a catalyst(such as BF₃ ether complex) in an allyl alcohol and dropping allylglycidyl ether into the obtained mixture at an elevated temperature(about 60° C.) to complete a reaction. Alternatively, some of suchadducts are commercially available (for example, an adduct of allylalcohol with 1 to 4 ethylene oxide units is commercially available underthe trade name of "Allyl glycol" (a product of Nippon Nyukazai Ltd.)).

Examples of the substituted or unsubstituted allyl alcohol to be used inthe above addition include allyl alcohol, crotyl alcohol,1-hydroxypentene-2, 1-hydroxyhexene-2, 1-hydroxyheptene-2,1-hydroxynonene-2, 1-hydroxydecene-2, 3-hydroxybutene-1,3-hydroxypentene-2, 2-hydroxyhexene-3, 3-hydroxy-2,3-dimethylbutene-1,4-hydroxy-2,3,4-trimethylpentene-2, and2-hydroxy-2,3,4,5-tetramethylhexene-3.

The epoxy-containing organic compound to be used in the above additionincludes ethylene oxide, propylene oxide, butylene oxide, allyl glycidylether, cyclohexane oxide, styrene oxide and epihalohydrin. Theseepoxy-containing organic compounds may be added alone or two or more ofthem may be added at rantom or in block. Preferable examples of theadduct include adducts of allyl alcohols with allyl glycidyl ether,adducts of allyl alcohols with allyl glycidyl ether and epichlorohydrin,adducts of allyl alcohols with allyl glycidyl ether and ethylene oxideand adducts of allyl alcohols with allyl glycidyl ether,epichloro-hydrin and ethylene oxide.

A preferable polyene compound represented by the above general formula(4) can be prepared by reacting the adduct of a substituted orunsubstituted allyl alcohol with an epoxy-containing organic compoundthus prepared with an acid anhydride or a polybasic acid. Moreparticularly, it can be prepared by the esterification of a commerciallyavailable adduct of allyl alcohol with ethylene oxide ("Allyl glycol"; aproduct of Nippon Nyukazai Co., Ltd.) with phthalic anhydride accordingto a conventional esterification process.

Examples of the acid anhydride or polybasic acid to be used in thepreparation of the polyene compound represented by the general formula(4) include maleic, succinic and hexahydrophthalic anhydrides andadipic, succinic, sebacic, phthalic, terephthalic, isophthalic, maleic,fumaric and iraconic acids.

The polyene compound represented by the general formula (4) alsoincludes compounds prepared by the following process. Namely, an adductof a substituted or unsubstituted allyl alcohol with an epoxy-containingorganic compound is reacted an acid anhydride or polybasic acid asdescribed above in such a way that part of the carboxylic acid remainsin an unreacted state and the remaining carboxylic acid is then reactedwith an unsaturated alcohol, with the proviso that this sequence ofreactions is conducted in such a way that at least one unit of the aboveadduct is present in each molecule. To illustrate the process moreparticularly, Allyl glycol which has been described above is reactedwith phthalic anhydride at an equivalent ratio of between 1.0:2.0 and1.9:2.0 (in a state wherein acid anhydride is excessive) to give apartial ester and the remaining carboxyl groups are then reacted withallyl alcohol to give an objective polyene compound. The unsaturatedalcohol includes not only allyl alcohol but also crotyl alcohol,3-hydroxybutene-1, 4-hydroxypentene-2, 2-hydroxyhexene-3,2-hydroxyheptene-3, 2-hydroxyoctene-3, 2,3-dimethyl-l-hydroxybutene-2,2,3-dimethyl-3-hydroxypentene-2, 4-hydroxybutene-1, 5-hydroxypentene-1,6-hydroxyheptene-1, 7-hydroxyheptene-1 and 8-hydroxyoctene-1.

The viscosity of the polyene compound represented by the general formula(4) at 50° C. is generally nearly 0 to 10000 P, preferably 1 to 1000 P.

The polyene compound represented by the general formula (5) is an adductof a mono- or poly-hydric alcohol or a saturated polyester polyol withallyl glycidyl ether containing at least two allyl glycidyl ether unitsper molecule on an average. Further adducts of a mono- or poly-hydricalcohol or a saturated polyester polyol with allyl glycidyl ether andone or more other three-membered ring epoxy compounds can be preferablyused. To illustrate the preparation of the polyene compound representedby the general formula (5) more particularly, the compound can be easilyprepared by incorporating BF₃ -ether complex as a catalyst in methanoland dropping allyl glycidyl ether into the obtained mixture at 60° C. tocomplete the reaction. The monohydric alcohol to be preferably used isan aliphatic, alicyclic, aromatic or O, N, S or halogen-containingalcohol having 1 to 15 carbon atoms and examples thereof includemethanol, ethanol, propanol, butanol, amyl alcohol, hexyl alcohol,octanol, 2-ethylhexanol, decanol, cyclohexanol, methoxyethanol,methylthioethanol, N,N-dimethylethanol, phenol, 2,6-dimethylphenol, andethylene chlorohydrin. The polyhydric alcohol include aliphatic,alcyclic, aromatic or O, N, or S-containing di- to hexa-hydric alcoholseach having 2 to 30 carbon atoms mentioned above with respect to thepolythiol compound (1). The saturated polyester polyol includes thoseeach having a molecular weight of 100 to 10000 and prepared by theesterification of a polyhydric alcohol as described above with acarboxylic acid such as succinic, adipic, sebacic phthalic,hexahydrophthalic, trimellitic or pyromellitic acid according to aconventional esterification process.

The three-membered ring epoxy compound to be arbitrarily used includesethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide,styrene oxide, and epihalohydrin, which may be used alone, as a mixtureof two or more of them, or together with allyl glycidyl ether.

The addition of the three-membered ring epoxy compound to water or thelike is conducted by the use of an acid catalyst such as sulfuric acid,BF₃ -ether complex or tin tetrachloride or a base catalyst such as NaOH,KOH or triethylamine according to a conventional process.

The viscosity of the polyene compound represented by the general formula(5) at 50° C. is generally nearly 0 to 10000 P, preferably 1 to 1000 P.

Triallyl cyanurate and triallyl isocyanurate each exhibit a viscosity ofas low as 200 cP or below at 25° C. and are excellent in reactivity uponirradiation with an actinic radiation such as ultraviolet rays by virtueof the presence of three actinic radiation-reactive carbon-to-carbondouble bonds therein, so that they can be used as a reactive diluent forthe actinic radiation-reactive pressure-sensitive adhesive compositionof the present invention.

These polyene compounds may be used either alone or as a mixture of twoor more of them.

Further, an acrylate resin having at least two actinicradiation-reactive carbon-to-carbon double bonds in the molecule is alsoparticularly preferably used as the polyene compound constituting theactinic radiation-curable resin according to the present invention.

The acrylate resin includes epoxy acrylate, urethane acrylate, polyesteracrylate, polyether acrylate, and esters of alcohols with acrylic acid.

The epoxy acrylate is preferably one prepared by the reaction of a knownaromatic, alicyclic or aliphatic epoxy resin with acrylic acid,particularly preferably an acrylate of an aromatic epoxy resin preparedby the reaction between acrylic acid and a polyglycidyl ether of apolyhydric phenol having at least one aromatic nucleus or an adductthereof with alkylene oxide. Particular examples thereof includeacrylates prepared by reacting a glycidyl ether prepared by the reactionbetween bisphenol A or an adduct thereof with alkylene oxide andepihalohydrin with acrylic acid; and acrylates prepared by the reactionbetween epoxy novolak resins and acrylic acid.

Preferable examples of the urethane acrylate include acrylates preparedby reacting one or two hydroxy-containing polyesters or polyethers withhydroxy-containing acrylates and isocyanates; and acrylates prepared bythe reaction of hydroxy-containing acrylates with isocyanates.

The hydroxy-containing polyester to be used in the preparation of theurethane acrylate is preferably one prepared by the esterification ofone or more polyhydric alcohols or adducts thereof with alkylene oxidewith one or more polybasic acids. Examples the polyhydric alcoholinclude 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, ethylene glycol,diethylene glycol, triethylene glycol, neopentyl glycol, polyethyleneglycol, polypropylene glycol, trimethylolpropane, pentaerythritol,dipentaerythritol, bisphenol A, hydrogenated bisphenol A, thiodiethanol,glycerin, triethanolamine, sorbitol, hydroquinone, pyrogallol, xyleneglycol, 4,4'-dihydroxydiphenylmethane, trishydroxyethyl isocyanurate andbishydroxyethylhydantoin. Examples of the polybasic acid includesuccinic, adipic, sebacic, phthalic, hexahydrophthalic, trimellitic andpyromellitic acids.

The hydroxy-containing polyether to be used therein is preferably oneprepared by the addition of one or more alkylene oxides to a polyhydricalcohol. Examples of the polyhydric alcohol include 1,3-butanediol,1,4-butanediol, 1,6-hexanediol, ethylene glycol, diethylene glycol,triethylene glycol, neopentyl glycol, polyethylene glycol, polypropyleneglycol, trimethylolpropane, pentaerythritol, dipentaerythritol,bisphenol A, hydrogenated bisphenol A, thiodiethanol, glycerin,triethanolamine, sorbitol, hydroquinone, pyrogallol, xylene glycol,4,4'-dihydroxydiphenylmethane, trishydroxyethyl isocyanurate, andbishydroxyethylhydantoin. The alkylene oxide includes ethylene oxide andpropylene oxide.

The hydroxy-containing acrylate is preferably one prepared by theesterification between a polyhydric alcohol and acrylic acid. Examplesof the polyhydric alcohol include 1,3-butanediol, 1,4-butanediol,1-6-hexanediol, ethylene glycol, diethylene glycol, triethylene glycol,neopentyl glycol, polyethylene glycol, polypropylene glycol,trimethylolpropane, pentaerythritol, dipentaerythritol, bisphenol A,hydrogenated bisphenol A, thiodiethanol, glycerin, triethanolamine,sorbitol, hydroquinone, pyrogallol, xylene glycol,4,4'-dihydroxydiphenylmethane, trishydroxyethyl isocyanurate, andbishydroxyethylhydantoin. Among these hydroxy-containing acrylates,those prepared by the esterification of aliphatic polyhydric alcoholswith acrylic acid are particularly preferable and examples thereofinclude 2-hydroxyethyl acrylate and pentaerythritol triacrylate.

Examples of the isocyanate include monomeric polyisocyanates such asdicyclohexylmethane 4,4'-diisocyanate, tolylene diisocyanate,diphenylmethane 4,4'-diisocyanate, xylylene diisocyanate, isophoronediisocyanate, and hexamethylene diisocyanate; and trimers of tolylenediisocyanate and isophorone diisocyanate.

The polyester acrylate is preferably one prepared by reacting ahydroxy-containing polyester with acrylic acid.

The hydroxyl-containing polyester to be used in the preparation of thepolyester acrylate is preferably one prepared by the esterification ofone or more polyhydric alcohols with one or more members selected fromamong monobasic acids, polybasic acids and phenols and examples of thepolyhydric alcohol included 1,3-butanediol, 1,4-butanediol,1,6-hexanediol, ethylene glycol, diethylene glycol, triethylene glycol,neopentyl glycol, polyethylene glycol, polypropylene glycol,trimethylolpropane, pentaerythritol, dipentaerythritol, bisphenol A,hydrogenated bisphenol A, thiodiethanol, glycerin, triethanolamine,sorbitol, hydroquinone, pyrogallol, xylene glycol,4,4'-dihydroxydiphenylmethane, trishydroxyethyl isocyanurate, andbishydroxyethylhydantoin. Examples of the monobasic acid include formic,acetic, butylcarboxylic and benzoic acids. Examples of the polybasicacid include succinic, adipic, sebacic, phthalic, hexahydrophthalic,trimellitic and pyromeltitic acids. The phenol includes phenol andp-nonylphenyol.

The polyether acrylate is preferably one prepared by reacting ahydroxyl-containing polyether with acrylic acid.

The hydroxyl-containing polyether to be used in the preparation of thepolyether acrylate is preferably one prepared by the addition of one ormore alkylene oxides to a polyhydric alcohol. Examples on the polyhydricalcohol include 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, ethyleneglycol, diethylene glycol, triethylene glycol, neopentyl glycol,polyethylene glycol, polypropylene glycol, trimethylolpropane,pentaerythritol, dipentaerythritol, bisphenol A, hydrogenated bisphenolA, thiodiethanol, glycerin, triethanolamine, sorbitol, hydroquinone,pyrogallol, xylene glycol, 4,4'-dihydroxydiphenylmethane,trishydroxyethyl isocyanurate, and bishydroxyethylhydantoin. Examples ofthe alkylene oxide include ethylene oxide and propylene oxide.

The acrylate of alcohol is preferably one prepared by reacting acrylicacid with an aromatic or aliphatic alcohol having at least one hydroxylgroup in the molecule or an adduct thereof with an alkylene oxide.Examples thereof include 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate,2-hydroxypropyl acrylate, isoamyl acrylate, lauryl acrylate, stearylacrylate, isooctyl acrylate, tetrahydrofurfuryl acrylate, isobornylacrylate, benzyl acrylate, 1,3-butanediol diacrylate, 1,4-butanedioldiacrylate, 1,6-hexanediol diacrylate, diethylene glycol diacrylate,triethylene glycol diacrylate, neopentyl glycol diacrylate, polyethyleneglycol diacrylate, polypropylene glycol diacrylate, trimethylolpropanetriacrylate, pentaerythritol triacrylate, and dipentaerythritolhexaacrylate.

The viscosity of the acrylate resin described above at 50° C. isgenerally nearly 0 to 10000 P, preferably 1 to 1000 P.

The curing of the acrylate resin is inhibited by oxygen in the air, sothat a low-molecular-weight acrylate monomer such as styrene isgenerally added to the resin in order to improve the curing rate, thoughsuch a low-molecular-weight acrylate monomer is generally highlyirritating to the skin.

The actinic radiation-reactive pressure-sensitive adhesive compositionof the present invention is characterized in that the actinicradiation-curable resin is constituted of a polyene compound having atleast two actinic radiation-reactive carbon-to-carbon double bonds inthe molecule, such as acrylate resins, and a polythiol compound, so thatthe curing of the composition is not inhibited by atmospheric oxygen.Accordingly, the use of a low-molecular-weight acrylate monomer isunnecessary, thus permitting the use of an acrylate resin which is oflow irritation to the skin. Such an acrylate resin which is of low tothe skin is desirably one having a molecular weight of 100 or above,more desirably 300 or above, and most desirably 500 or above.

These polyene compounds described above may De used either alone or as amixture of two or more of them.

In the actinic radiation-reactive pressure-sensitive adhesivecomposition of the present invention, the actinic radiation-curableresin is preferably contained in an amount of 1 to 500 parts by weightper 100 parts by weight of the pressure-sensitive adhesive organiccompound used. Particularly, one comprising 10 to 200 parts by weight ofthe actinic radiation-curable resin and 100 parts by weight of theorganic compound exhibits excellent characteristics.

In the actinic radiation-reactive pressure-sensitive adhesivecomposition of the present invention, a plurality of each of thepressure-sensitive adhesive organic compound and both of the polythiolcompound and polyene compound constituting the actinic radiation-curableresin can be used in order to attain the characteristics desirable as anactinic radiation-reactive pressure-sensitive adhesive composition.

When the ratio of the curable resin to the organic compound is too low,the resulting composition will exhibit a low degree of reduction in theadhesive force upon irradiation with an actinic radiation such asultraviolet rays and therefore the adhesive force cannot be lowered to100 g/20 mm or below after irradiation, so that the pickup in themounting step cannot be easily conducted, though the adhesive force (90°peel strength at a peel rate of 50 mm/min) thereof for a semiconductorwafer is sufficient before irradiation. On the contrary, when this ratiois too high, the adhesive force (90° peel strength at a peel rate of 50mm/min) thereof for a semiconductor wafer will be insufficient, evenbefore the irradiation with an actinic radiation such as ultravioletrays, so that the wafer will be unfavorably shifted or peeled of in thedicing step.

The formulation of the actinic radiation-curable resin which is one ofthe components constituting the actinic radiation-reactivepressure-sensitive adhesive composition of the present invention willnow be described.

The actinic radiation-curable resin comprises one or more polythiolcompounds and one or more polyene compounds, each having at least twoactinic radiation-reactive carbon-to-carbon double bonds in the moleculeas the essential components.

The polythiol compound and the polyene compound are preferably used insuch amounts that the equivalent ratio of the carbon-to-carbon doublebond to the thiol group lies between 0.7:1.0 and 1.5:1.0. When thisratio is near 1.0:1.0, particularly desirable results can be obtained.

According to the present invention, the curing of the actinicradiation-curable resin can be conducted by irradiation with an actinicradiation, followed by, if necessary, heating. The actinic radiationincludes visible rays, ultraviolet rays, electron beams, and X-rays.

When the actinic radiation-curable resin is to be cured with ultravioletrays, an ultraviolet cure initiator is added to a mixture comprising thepolythiol compound and the polyene compound as described above in orderto induce the curing.

The ultraviolet cure initiator includes keto, azide, azo, diazo andperoxide compounds. Examples of the keto compound includediethoxyacetophenone, 2-hydroxymethyl-1-phenylpropan-1-one,4'-isopropyl-1-hydroxy-2-methylpropiophenone,2-hydroxy-2-methylpropiophenone, p-dimethylaminoacetophenone,p-t-butyldichloroacetophenone, p-t-butyltrichloroacetophenone,p-azidobenzalacetophenone, benzoin, benzoin methyl ether, benzoin ethylether, benzoin isopropyl ether, benzoin n-butyl ether, benzoin isobutylether, benzil, benzil dimethyl ketal, benzil-β-methoxyethyl acetal,1-hydroxycylcohexyl phenyl ketone, benzophenone, methylo-benzoylbenzoate, Michler's ketone, 4,4'-bisdiethylaminobenzophenone,4,4'-dichlorobenzophenone, thioxanthone, 2-methylthioxanthone,2-ethylthioxanthone, 2-chlorothioxanthone, and 2-isopropylthioxanthone.The azide compound includes 4,4'-diazidostilbene andp-phenylenebisazide. The azo compound includes2,2'-azobisisobutyronitrile and 2,2'-azobisdimethylvaleronitrile. Thediazo compound includes diazoaminobenzene. The peroxide compoundincludes di-t-butyl peroxide.

Although the amount of the ultraviolet cure initiator to be added may besuitably selected depending upon the kind thereof, it is preferably 0.1to 20 parts by weight per 100 parts by weight of the mixture comprisingthe polythiol compound and the polyene compound. When the amount of theultraviolet cure initiator is less than 0.1 part by weight per 100 partsby weight of the mixture, the resulting actinic radiation-reactivepressure-sensitive adhesive composition will be poor in reactivity uponirradiation with ultraviolet rays to give a low degree of reduction inthe adhesive force and therefore, the adhesive force cannot be loweredto 100 g/20 mm or below, so that the pickup in the mounting step willnot be facilitated, though the adhesive force (90° peel strength at apeel rate of 50 mm/min) thereof for a semiconductor wafer will besufficient before the irradiation. On the contrary, when this amountPG,42 exceeds 20 parts by weight, the adhesive force (90° peel strengthat a peel rate of 50 mm/min) of the resulting adhesive composition for asemiconductor wafer will be insufficient even before the irradiationwith an actinic radiation such as ultraviolet rays, so that the waferwill be shifted or peeled of in the dicing step. Further, theultraviolet cure initiator will unfavorably remain on the chips preparedby dicing the wafer even after the pickup.

These ultraviolet cure initiators may be used alone or as a mixture twoor more of them depending upon the required performance.

If necessary, the actinic radiation-reactive pressure-sensitive adhesivecomposition of the present invention may contain a crosslinking agentfor the adhesive organic compound.

The crosslinking agent is preferably a compound which is reactive withthe functional group contained in the adhesive organic compound, such asa hydroxyl or carboxyl group, and examples thereof include melaminecompound, isocyanate compound, acid anhydride, amine compound, epoxyresin, and phenolic resin.

The crosslinking agent is a compound which is reactive with thefunctional group contained in the adhesive organic compound, such as ahydroxy or carboxyl group, and serves to control the adhesive force ofthe composition of the present invention. That is, the actinicradiation-reactive pressure-sensitive adhesive composition of thepresent invention is improved in adhesive force by incorporating acrosslinking agent thereinto, though the composition exhibits anacceptable adhesive force even if it contains no crosslinking agent.

The amount of the crosslinking agent is preferably 20 parts by weight orbelow per 100 parts by weight of the organic compound. The actinicradiation-reactive pressure-sensitive adhesive composition of thepresent invention has an acceptable adhesive force even when it does notcontain any crosslinking agent and the adhesive force can be furtherimproved by incorporating a crosslinking agent into the composition.However, the use of a crosslinking agent in an amount exceeding 20 partsby weight per 100 parts by weight of the organic compound isunfavorable, because part of the crosslinking agent remains withoutbeing consumed during the crosslinking of the organic compound to lowerthe adhesive force thereof.

The crosslinking agent may be used alone or as a mixture of two or moreof them depending upon the required performance.

If necessary, the pressure-sensitive adhesive composition of the presentinvention may contain a tackifier.

Preferred examples of the tackifier include ester gum, polyterpeneresin, terpene-phenol resin, polyolefin resin, polystyrene resin,cyclopentadiene resin, aromatic petroleum resin, cumarone-indenestyreneresin, cumarone-indene resin, xylene resin, modified phenolic resin,alkylphenolic resin, alkylphenol-acetytene resin, dammar, rosin, rosinderivative and DCPD petroleum resin.

Although the pressure-sensitive adhesive composition of the presentinvention exhibits an acceptable adhesive force, even when it does notcontain any tackifier, the adhesive force can be further improved byincorporating a tackifier into the composition.

The amount of the tackifier is preferably 200 parts by weight or belowper 100 parts by weight of the organic compound. The pressure-sensitiveadhesive composition of the present invention has an acceptable adhesiveforce even when it does not contain any tackifier and the adhesive forcecan be further improved by incorporating a tackifier into thecomposition. However, the use of a tackifier in an amount exceeding 200parts by weight per 100 parts by weight of the organic compoundunfavorably brings about a lowering in its adhesive force.

The tackifier may be used alone or as a mixture of two or more of themdepending upon the required performance.

Thermosettability can be imparted to the actinic radiation-reactivepressure-sensitive adhesive composition of the present invention by theaddition of a free radical generator. The free radical generatorincludes peroxides, azo compounds and combinations of peroxides anddecomposition accelerators.

Examples of the peroxide include ketone peroxides such as methyl ethylketone peroxide and cyclohexanone peroxide; diacyl peroxides such asbenzoyl peroxide and lauroyl peroxide; hydroperoxides such as t-sutylhydroperoxide and cumene hydroperoxide; dialkyl peroxides such asdi-t-butyl peroxide and dicumyl peroxide; alkyl peresters such ast-butyl perbenzoate; and inorganic peroxides such as lead peroxide andmanganese peroxide. Examples of the azo compound include2,2'-azobisisobutyronitrile, 2,2'-azobisdimethylvaleronitrile and2,2'-azobis(2,3,3-trimethylbutyronitrile). Further, a peroxide may beused together with a salt of a heavy metal such as cobalt, manganese,iron or copper or a tertiary amine such as dimethylaniline ordimethyl-p-toluidine as a decomposition accelerator.

Although the amount of the free radical generator may be suitablyselected depending upon the kind thereof, it is preferably 50 parts byweight or below, still preferably 30 parts by weight or below per 100parts by weight of the mixture of the polythiol compound with thepolyene compound. The addition of the free radical generator in anamount exceeding 50 parts by weight per 100 parts by weight of themixture unfavorably brings about an adverse effect such as retardationof curing.

The free radical generator may be used alone or as a mixture of two ormore of them depending upon the required performance.

The pressure-sensitive adhesive composition of the present invention canbe improved in the curing rate by incorporating an accelerator into thecomposition. Amine compounds are preferably used as such an acceleratorand examples thereof include monoethanolamine, diethanolamine,triethanolamine, 4,4'-bisdiethylaminobenzophenone, ethyl4-dimethylaminobenzoate, isopentyl 4-dimethylaminobenzoate and2-dimethylaminoethyl benzoate; high-molecular-weight amine compoundsprepared from epoxy resins and amine compounds; and derivatives of theabove amine compounds, such as triethanolamine triacrylate.

Although the amount of the accelerator may be suitably selecteddepending upon the kind thereon, it is preferably 50 parts by weight orbelow, still preferably 30 parts by weight or below per 100 parts byweight of the mixture of the polythiol compound with the polyenecompound. The addition of the accelerator in an amount exceeding 50parts by weight per 100 parts by weight of the mixture unfavorablybrings about an adverse effect such as retardation of curing.

The accelerator may be used alone or as a mixture of two or more of themdepending upon the required performance.

The pressure-sensitive adhesive composition of the present invention mayfurther contain a stabilizer to thereby lengthen the pot life.

Examples of the stabilizer include quaternary ammonium chloride such asbenzyltrimethylammonium chloride, diethylhydroxylamine, cyclic amine,nitrile compound, substituted urea, benzothiazole,4-amino-2,2,6,6-tetramethylpiperidine,bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate; organic acids such aslactic, oxalic, citric, tartaric and benzoic acids; hydroquinone andalkyl ethers thereof; t-butylpyrocatechol, phosphorus acid compoundssuch as tridecyl phosphite; organic phosphine, phosphorous acid salts;copper compounds such as copper naphthenate and an adduct oftrichloroethyl phosphite with cuprous chloride; and caprylates of ironor manganese, naphthenates and sulfoxides.

Although the pressure-sensitive adhesive composition of the presentinvention exhibits a pot life of 6 months or longer in a dark place at20° C. even if it does not contain any stabilizer, and is practicallyproblem-free in this respect, the pot life thereof can be lengthened to12 months or longer by the addition of the stabilizer. The amount of thestabilizer used is preferably 50 parts by weight or below, stillpreferably 30 parts by weight or below, per 100 parts by weight of themixture of the potythiol compound with the polyene compound, though itmay be suitably selected depending upon the kind thereof. The use of thestabilizer in an amount exceeding 50 parts by weight per 100 parts byweight of the mixture remarkably lowers the curing rate unfavorably.

The stabilizer may be used alone or as a mixture of two or more of themdepending upon the required performance.

Further, the pressure-sensitive adhesive composition of the presentinvention may contain an ultraviolet absorber to thereby lengthen itspot life under fluorescent lighting.

Examples of the ultraviolet absorber include benzophenones such as2-hydroxybenzophenone, 2,4-dihydroxybenzophenone,2-hydroxy-4-methoxybenzophenone, 2,2',4-trihydroxybenzophenone,2,2'-dihydroxy-4-methoxybenzophenone and2,2',4,4'-tetrahydroxybenzophenone; salicylates such as phenylsalicylate and 2,4-di-t-butytphenyl 3,5-di-t-butyl-4-hydroxybenzoate;benzotriazoles such as (2'-hydroxyphenyl)benzotriazole,(2'-hydroxy-5'-methylphenyl)benzotriazole,(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole;acrylonitriie compounds such as ethyl 2-cyano-3,3-diphenylacrylate andmethyl 2-carbomethoxy-3-(p-methoxy)acrylate; metal complexes such asnickel. [2,2'-thiobis(4-t-octyl)phenolate] n-butylamine, nickeldibutyldithiocarbamate and cobalt dicyctohexyl dithiophosphate; andhindered amines such as bis(2,2,6,6-tetramethylpiperidinyl-4) sebacate.

Although the pressure-sensitive adhesive composition of the presentinvention exhibits a pot life of 2 weeks or longer at 20° C. underfluorescent lighting, even when it does not contain any ultravioletabsorber, and thus is practically in this respect, the pot life thereofcan be lengthened to one month or longer by the addition of anultraviolet absorber. The amount of the ultraviolet absorber to be addedis preferably 50 parts by weight or below, still preferably 30 parts byweight or below per 100 parts by weight of the mixture of the polythiolcompound with the polyene compound, though it may be suitably selecteddepending upon the kind thereof. The use of the ultraviolet absorber inan amount exceeding 50 parts by weight per 100 parts by weight of themixture remarkably lowers the curing rate unfavorably.

The ultraviolet absorber may be used alone or as a mixture of two ormore of them depending upon the required performance.

If necessary, the pressure-sensitive adhesive composition of the presentinvention may contain a filler.

Preferred examples of the filler include zinc oxide, titanium oxide,silica, aluminum hydroxide, calcium carbonate, barium sulfate, clay, andtalc.

Although the pressure-sensitive adhesive composition of the presentinvention exhibits an acceptable adhesive force even if it does notcontain any filler, the adhesive force thereof can be further improvedby the addition of the filler.

The amount of the filler to be used is preferably 200 parts by weight orbelow per 100 parts by weight of the pressure-sensitive adhesive organiccompound. The pressure-sensitive adhesive composition of the presentinvention exhibits an acceptable adhesive force even when it does notcontain any filler, and the adhesive force thereof can be furtherimproved by the addition of the filler. However, the use of the fillerin an amount exceeding 200 parts by weight per 100 parts by weightof-the organic compound lowers the adhesive force unfavorably.

The filler may be used alone or as a mixture of two or more of themdepending upon the required performance.

The pressure-sensitive adhesive composition of the present invention maycontain, if necessary, other additives so far as the effect of thepresent invention is not damaged. Examples of the additives includecoloring agents such as pigments and dyes, anti-foaming agents, levelingagents, thickeners, flame retardants, plasticizers, and solvents.

The practical application of the pressure-sensitive adhesive compositionof the present invention is conducted as follows: First, the compositionis uniformly applied to an optically transmissive film having athickness of 5 to 200 μm and made from a plastic such as polyvinylchloride, polyethylene terephthalate, polyethylene, polypropylene orcrosslinked polyolefin in a thickness of 1 to 50 μm to prepare apressure-sensitive adhesive sheet exhibiting an adhesive force (90° peelstrength at a peel rate of 50 mm/min) of 200 to 1000 g/20 mm for asemiconductor wafer. In this step, the adhesive force may be regulatedby heating if necessary. Then, a semiconductor wafer is diced into chipswhile being fixed on this sheet. The dicing may be conducted by anyknown process such as diamond scribing, laser scribing or blade dicing.Thereafter, the thus treated sheet is irradiated with an actinicradiation from the plastic film side to cure the adhesive composition.After the adhesive force has been lowered thereby to 100 g/20 mm orbelow, the chips are picked up and mounted on a base. The actinicradiation includes ultraviolet rays, electron seams, X-rays, radioactiveradiation, and radiofrequency radiation. Among these actinic radiations,ultraviolet rays and electron beams are preferable. The source of theultraviolet rays includes mercury vapor lamp, xenon lamp, sodium lamp,alkali metal lamp and ultraviolet laser, while the electron beams can begenerated with an accelerator. The irradiation time varies dependingupon the kind and output powder of the actinic radiation and formulationof the actinic radiation-reactive pressure-sensitive adhesivecomposition. For example, when a high-pressure mercury vapor lamp of 80W/cm is used at a distance of 20 cm, the adhesive force can be loweredto 100 g/20 mm or below by the irradiation for 0.5 to 20 seconds. Themounting may be conducted by any known process such as eutectic alloyjointing, wax jointing or resin jointing.

The actinic radiation-reactive pressure-sensitive adhesive compositionof the present invention is characterized in that the actinicradiation-curable resin contained therein is constituted of one or morepolythiol compounds and one or more polyene compounds each having atleast two actinic radiation-reactive carbon-to-carbon double bonds inthe molecule, so that it exhibits a high reactivity upon irradiationwith an actinic radiation and that the curing of the composition is nothindered by oxygen to give an extremely high curing rate in the air.

Up to this time, various acrylate resins such as polyester acrylate,urethane acrylate, epoxy acrylate and polyether acrylate resins havebeen used as the actinic radiation-curable resin for the actinicradiation-reactive pressure-sensitive adhesive composition in the dicingof a semiconductor wafer. However, when the dicing is conducted in theair by using such an acrylate resin a process which comprises conductingthe irradiation with a high-output actinic radiation exposure system fora prolonged time or a process which comprises conducting the dicing inan inert gas such as nitrogen or a vacuum must be employed, because thecuring of the resin is significantly inhibited by oxygen. Further, theseprocesses have disadvantages in that the dicing takes a prolonged timeand that enlarged and complicated equipment is necessary.

As described above, the actinic radiation-reactive pressure-sensitiveadhesive composition of the present invention is characterized in thatthe actinic radiation-curable resin contained therein is constituted ofone or more polythiol compounds and one or more polyene compounds eachhaving at least two actinic radiation-reactive carbon-to-carbon doublebonds in the molecule. Therefore, the composition exhibits a highreactivity upon irradiation with an actinic radiation and the curing ofthe composition is not inhibited by oxygen, thus giving an extremelyhigh curing rate in the air. Accordingly, the composition has advantagesin that the adhesiveness of the composition can be lost or lowered byirradiation for a shortened time and that the dicing can be conductedwith simple and small equipment, because it can be conducted in air.

Further, according to the present invention, an actinicradiation-reactive pressure-sensitive adhesive composition which is freefrom the problem of inhibition of curing by oxygen can be obtainedwithout using any functional monomer or diluent which is irritating tothe skin and very smelly, though the acrylate resins of the prior arthave a problem in that the use of such a monomer or diluent forimproving the reactivity of the resin in air brings about irritation tothe skin and odor. Thus, the composition of the present invention isvery safe in respect of handleability.

EXAMPLES

Representative embodiments of the present invention will now bedescribed in more detail by referring to the following Examples, thoughthe present invention is not limited by them. In the Examples andComparative Examples, all formulations are given by part by weight.

Examples 1 To 11

The formulations of the actinic radiation-reactive pressure-sensitiveadhesive compositions of Examples 1 to 11 and the results of theexamination thereof for adhesive force are given in Table 1. Detaileddescriptions of the pressure-sensitive adhesive organic compound and thecomponents of the actinic radiation-curable resin are given in Table 2.Since no adducts of allyl alcohol with epoxy compounds were commerciallyavailable, those prepared in a laboratory were used (Polyenes 1 to 4).The preparation procedures thereof will be described in the item"Synthesis of polyene compounds". The other components were allcommercially available ones. The equivalent ratio of the actinicradiation-reactive carbon-to-carbon double bond contained in the polyenecompound to the thiol group contained in the polythiol compound wasalways 1.0:1.0.

The adhesive force was determined by the following procedure: Each ofthe actinic radiation-reactive pressure-sensitive adhesive compositionsof Examples 1 to 11 was uniformly applied on a polyvinyl chloride sheethaving a thickness of 100 μm in a coating thickness of 20 μm and heatedat 40° C. for 30 hours to give a pressure-sensitive adhesive sheet. Thissheet was cut into 20 mm wide pieces and stuck to a semiconductor waferto determine its adhesive force before irradiation with an actinicradiation. The adhesive force was determined by measuring the peelstrength at a peel angle of 90° and at a peel rate of 50 mm/min.Thereafter, the wafer-sheet laminate was irradiated with ultravioletrays from the polyvinyl chloride sheet side in the air by the use of ahigh-pressure mercury vapor lamp of 80 W/cm placed at a distance of 20cm from the laminate for 3 seconds (Examples 1 to 7 and 9 to 11) or 1.5seconds Example 8) to determine the adhesive force in a similar mannerto that described above.

                                      TABLE 1                                     __________________________________________________________________________                       Ex. Ex. Ex. Ex. Ex. Ex. Ex. Ex. Ex. Ex. Ex.                Components         1   2   3   4   5   6   7   8   9   10  11                 __________________________________________________________________________    acrylic adhesive compound 1                                                                      100 100 100 100 100 100 100 100 100                        acrylic adhesive compound 2                            100                    saturated polyester adhesive compound                      100                Polyene 1          29.5            12.6                                                                              27.6                                                                              29.5                                                                              29.5                                                                              29.5                                                                              59.0                                                                              59.0               Polyene 2              35.0                                                   Polyene 3                  39.2                                               Polyene 4                      27.0                                           Polyene 5                          12.6                                       thiol 1            20.5                                                                              15.0                                                                              10.8                                                                              23.0                                                                              24.8    20.5                                                                              20.5                                                                              20.5                                                                              41.0                                                                              41.0               thiol 2                                22.4                                   ultraviolet cure initiator                                                                       2.0 2.0 2.0 2.0 3.0 3.0 5.0 5.0 5.0 10.0                                                                              10.0               crosslinking agent                         5.0                                accelerator                                    5.0                            filler                                             30.0                       adhesive force                                                                g/20 mm                                                                       before irradiation 500 600 550 400 350 650 800 500 800 500 450                after irradiation  50  60  50  30  60  60  50  30  60  50  70                 irradiation time (sec)                                                                           3.0 3.0 3.0 3.0 3.0 3.0 3.0 1.5 3.0 3.0 3.0                __________________________________________________________________________

                  TABLE 2                                                         ______________________________________                                        Component          Description                                                ______________________________________                                        acrylic adhesive       butyl acrylate-acrylic acid                            compound 1             copolymer                                              acrylic adhesive       butyl acrylate-                                        compound 2             acrylonitrile acrylic acid                                                    copolymer                                              saturated polyester    terephthalic acid/sebacic                              adhesive compound      acid/ethylene glycol                                                          copolymer                                              Polyene 1              derivatives of adducts                                 Polyene 2              of allyl alcohol with                                  Polyene 3              epoxy compounds (see                                   Polyene 4              the item of "Synthesis                                                        of polyene compounds")                                 Polyene 5              trially isocyanurate                                   thiol 1                pentaerythritol tetrakis-                                                     thioglycolate                                          thiol 2                pentaerythritol tetrakis-β-                                              mercaptopropionate                                     ultraviolet cure       2-hydroxymethyl-1-                                     initiator              phenylpropan-1-one                                     crosslinking agent     tolylene diisocyanate                                  accelerator            isopentyl 4-dimethyl-                                                         aminobenzoate                                          filler                 zinc oxide                                             ______________________________________                                    

Synthesis of Polyene Compounds

Polyenes 1 to 4 were prepared by the procedure which will be describedbelow. The raw materials used are listed in Table 3.

                  TABLE 3                                                         ______________________________________                                        Polyene                   Charge  General                                     No.      Raw materials    (g)     formula                                     ______________________________________                                        1        allyl alcohol    58      (2)                                                  allyl glycidyl ether                                                                           228                                                          epichlorohydrin  185                                                          BF.sub.3 -ether complex                                                                        0.5                                                          (catalyst)                                                           2        dicyclohexylmethane                                                                            131     (3)                                                  4,4'-diisocyanate                                                             adduct of allyl alcohol                                                                        120                                                          with ethylene oxide                                                           dibutyltin dilaurate                                                                           0.8                                                          (catalyst)                                                           3        Polyene 1        47.1    (4)                                                  allyl alcohol    10.5                                                         phthalic anhydride                                                                             11.8                                                         benzene          50                                                           BF.sub.3 -ether complex                                                                        0.5                                                          (catalyst)                                                                    p-toluenesulfonic                                                                              0.4                                                          acid (catalyst)                                                      4        methanol         32      (5)                                                  allyl glycidyl ether                                                                           285                                                          BF.sub.3 -ether complex                                                       (catalyst)       0.5                                                 ______________________________________                                    

Polyene 1

58 g (1 mol) of allyl alcohol and 0.5 g of BF₃ -ether complex were fedinto a nitrogen-purged 500-cc four-necked flask (fitted with a condenserand a dropping funnel). 228 g (2 mol) of allyl glycidyl ether wasdropped into the flask over a period of 3 hours, while keeping thecontents at 60° to 70° C. Further, 185 g (2 mol) of epichlorohydrin wasdropped into the flask at that temperature. This dropping took 2.5hours. After the completion of the dropping, the contents were stirredfor one hour, while keeping them at 70° C., to conduct a reaction. Afterthe completion of the reaction, the reaction mixture was deaerated in avacuum of 3 mmHg at 70° C. for one hour. Nearly no low-boiling matterwas recovered. The obtained product was a colorless transparent liquidhaving a viscosity (25° C.) of 50 cP or below.

Polyene 2

131 g (0.5 mol) of dicyclohexylmethane 4,4'-diisocyanate (Hylene W, aproduct of Du Pont) was placed in a flask in a nitrogen atmosphere,followed by the addition of 0.8 g dibutyltin dilaurate. The contentswere heated to 45° C. 120 g (1.0 mol) of an adduct of allyl alcohol withethylene oxide (Allyl glycol, a product of Nippon Nyukazai Co., Ltd.)was dropped into the flask through a dropping funnel in such a way as tokeep the contents at 80° to 90° C. After the completion of the dropping,the mixture was kept at 80° to 90° C. for 2 hours to conduct a reaction.The IR spectrum of the obtained product revealed the completedisappearance of the isocyanate group, which means the formation ofurethane linkage.

Polyene 3

47.1 g (0.1 mol) of Polyene 1, 11.8 g (0.08 mol) of phthalic anhydride,50 g of benzene and 0.4 g of p-toluenesulfonic acid were placed in a200-cc four-necked flask and reacted under the reflux of the benzene for2 hours, followed by the addition of 10.5 g (0.18 mol) of allyl alcohol.The obtained mixture was subjected to azeotropic dehydration. After thecompletion of the dehydration, the resulting mixture was neutralizedwith a 10% aqueous solution of NaHCO₃. The obtained organic layer wasfreed from the solvent and deaerated in a vacuum of 2 mmHg at 90° C. forone hour.

Polyene 4

32.0 g (1 mol) of methanol and 0.5 g of BF₃ -ether complex were fed intoa 500-cc four-necked flask fitted with a condenser. 285 g (2.5 mol) ofallyl glycidyl ether was dropped into the flask over a period of 4hours, while keeping the mixture at 50° to 60° C. by stirring. After thecompletion of the dropping, the mixture was further stirred for one hourat 60° C. to complete the reaction. The reaction mixture was gaschromatographed to detect either unreacted methanol nor unreacted allylglycidyl ether.

As apparent from the results given in Table 1, the adhesive force beforethe irradiation with an antinic radiation of the pressure-sensitiveadhesive sheets prepared by using the actinic radiation-reactivepressure-sensitive adhesive compositions of Examples 1 to 11 all fell inthe range of 200 to 1000 g/20 mm, while the adhesive forces were alllowered to 100 g/mm or below by the irradiation with ultraviolet rays.Thus, the pressure-sensitive adhesive sheets have performances enablingthem to be used in the dicing of a semiconductor wafer.

In Example 7, a crosslinking agent was used so that the adhesive forcebefore the irradiation was enhanced. In Example 8, an accelerator wasused so that the curing rate was enhanced to shorten the irradiationtime to 1.5 seconds. In Example 9, a filler was used so that theadhesive force before the irradiation was enhanced.

Further, a semiconductor wafer having a diameter of 5 inch was stuck toa pressure-sensitive adhesive sheet prepared by using each of theadhesive compositions of Examples 1 to 11 and diced into chips 50 mmsquare with a rotary circular blade. In a case wherein any of thecompositions of Examples 1 to 11 was used, the dicing could beaccurately conducted without causing the shift or peeling of the wafer.After the irradiation with ultraviolet rays had been conducted under thesame conditions as those of the above test on adhesive force, the chipswere easily picked up by sticking up with a needle in all of theExamples 1 to 11.

Comparative Examples 1 To 4

The formulations of the actinic radiation-reactive pressure-sensitiveadhesive compositions of Comparative Examples 1 to 4 and the results ofthe examination thereof for adhesive force are given in Table 4. Thepressure-sensitive adhesive organic compounds and ultraviolet cureinitiator used are the same as those used in Examples 1 to 11, while apolyester acrylate or a urethane acrylate was used as the actinicradiation-curable resin.

The obtained pressure-sensitive adhesive sheets were examined in asimilar manner to that of Examples 1 to 11. The adhesive forces of thesheets before the irradiation all fell in the range of 200 to 1000 g/20mm. However, the adhesive force could not be lowered to 100 g/20 mm orbelow by the irradiation with ultraviolet rays, though the irradiationtime was 10 seconds, which was longer than that of the foregoingExamples, because the curing was inhibited by atmospheric oxygen toresult in insufficient progress thereof. In Comparative Example 2,particularly, the adhesive force was not lowered at all.

In a similar manner to that of Examples 1 to 11, a semiconductor waferhaving a diameter of 5 inch was stuck to a pressure-sensitive adhesivesheet prepared by using each of the compositions of Comparative Examples1 to 4 and diced into chips 50 mm square with a rotary circular blade.In a case wherein any of the compositions of Comparative Examples 1 to 4was used, the dicing could be accuracy conducted without causing theshift or peeling of the wafer. After the irradiation with ultravioletrays had been conducted in a similar manner to that of Examples 1 to 11for 10 seconds, the chips were picked up. In a case wherein any of thecompositions of Comparative Examples 1 to 4 was used, the pickup couldnot be easily conducted. Further, the chip picked-up had the adhesivecomposition adhered thereto. Thus, the pressure-sensitive adhesivesheets of Comparative Examples 1 to 4 do not satisfy the performancenecessitated as the sheet to be used in the dicing of a semiconductorwafer.

                  TABLE 4                                                         ______________________________________                                                     Comp.     Comp.   Comp    Comp.                                  Components   Ex. 1     Ex. 2   Ex. 3   Ex. 4                                  ______________________________________                                        acrylic adhesive                                                                           100       100                                                    compound 1*.sup.1                                                             acrylic adhesive               100                                            compound 2*.sup.1                                                             saturated polyester                    100                                    adhesive compound*.sup.1                                                      acrylate resin 1*.sup.2                                                                    50                100     100                                    acrylate resin 2*.sup.3                                                                              50                                                     ultraviolet cure                                                                           5.0       5.0     5.0     5.0                                    initiator*.sup.1                                                              adhesive                                                                      force g/20 mm                                                                 before       550       500     600     450                                    irradiation                                                                   after                                                                         irradiation  400       500     300     300                                    irradiation time (sec)                                                                     10.0      10.0    10.0    10.0                                   ______________________________________                                         note)                                                                         *.sup.1 the same as those used in Examples 1 to 11                            *.sup.2 dipentaerythritol hexaacrylate                                        *.sup.3 urethane acrylate prepared from hexamethylene diisocyanate and        2hydroxyethyl acrylate                                                   

Examples 12 To 20

The formulations of the actinic radiation-reactive pressure-sensitiveadhesive compositions of Examples 12 to 20 and the results of theexamination thereof for adhesive force are given in Table 5. Thepressure-sensitive adhesive organic compound used ant the constituentsof the actinic radiation-curable resin used are given in Table 6 indetail. The components used are all commercially available ones. Theequivalent ratio of the actinic radiation-reactive carbon-to-carbondouble bond contained in the polyene compound to the thiol groupcontained in the polythiol compound was always 1.0:1.0.

The examination was conducted by the same procedure as that of Examples1 to 11.

                                      TABLE 5                                     __________________________________________________________________________                       Ex. Ex. Ex. Ex. Ex. Ex. Ex. Ex. Ex.                        Components         12  13  14  15  16  17  18  19  20                         __________________________________________________________________________    acrylic adhesive compound 1                                                                      100 100 100 100 100 100 100                                acrylic adhesive compound 2                    100                            saturated polyester adhesive compound              100                        Polyene 6          22.8    11.1                                                                              21.3                                                                              22.8                                                                              22.8                                                                              22.8                                                                              45.6                                                                              45.6                       Polyene 7              28.8                                                   Polyene 8                  11.1                                               thiol 3            27.2                                                                              21.2                                                                              27.8    27.2                                                                              27.2                                                                              27.2                                                                              54.4                                                                              54.4                       thiol 4                        28.7                                           ultraviolet cure initiator                                                                       2.0 2.0 3.0 3.0 5.0 5.0 5.0 10.0                                                                              10.0                       crosslinking agent                 5.0                                        accelerator                            5.0                                    filler                                     30.0                               adhesive force                                                                g/ 20 mm                                                                      before irradiation 700 500 350 650 800 500 800 500 450                        after irradiation  60  50  60  60  50  30  60  50  70                         irradiation time (sec)                                                                           3.0 3.0 3.0 3.0 3.0 1.5 3.0 3.0 3.0                        __________________________________________________________________________

                  TABLE 6                                                         ______________________________________                                        Component        Description                                                  ______________________________________                                        acrylic adhesive butyl acrylate-acrylic acid                                  compound 1       copolymer                                                    acrylic adhesive butyl acrylate                                               compound 2       acrylonitrile-acrylic acid                                                    copolymer                                                    saturated polyester                                                                            terephthalic acid/sebacic                                    adhesive compound                                                                              acid/ethylene glycol                                                          copolymer                                                    Polyene 6        dipentaerythritol                                                             hexaacrylate                                                 Polyene 7        urethane acrylate prepared                                                    from hexamethylene                                                            diisocyanate and 2-                                                           hydroxyethyl acrylate                                        Polyene 8        triallyl isocyanurate                                        thiol 3          pentaerythritol                                                               tetrakisthioglycolate                                        thiol 4          pentaerythritol tetrakis-                                                     β-mercaptopropionate                                    ultraviolet cure 2-hydroxymethyl-1-phenyl-                                    initiator        propan-1-one                                                 crosslinking agent                                                                             tolylene diisocyanate                                        accelerator      isopentyl 4-dimethyl-                                                         aminobenzoate                                                filler           zinc oxide                                                   ______________________________________                                    

As apparent from the results given in Table 5, the adhesive forcesbefore the irradiation with an antinic radiation of thepressure-sensitive adhesive sheets prepared by using the actinicradiation-reactive pressure-sensitive adhesive compositions of Examples12 to 20 all fell in the range of 200 to 1000 g/20 mm while the adhesiveforces were all lowered to 100 g/mm or below by the irradiation withultraviolet rays. Thus, the pressure-sensitive adhesive sheets haveperformances enabling them to be used in the dicing of a semiconductorwafer.

In Example 16, a crosslinking agent was used so that the adhesive forcebefore irradiation was enhanced. In Example 17, an accelerator was usedso that the curing rate was enhanced to shorten the irradiation time to1.5 seconds. In Example 18, a filler was used so that the adhesive forcebefore irradiation was enhanced.

Further, a semiconductor wafer having a diameter of 5 inch was stuck toa pressure-sensitive adhesive sheet prepared by using each of theadhesive compositions of Examples 12 to 20 and diced into chips 50 mmsquare with a rotary circular blade. In a case wherein any of thecompositions of Examples 12 to 20 was used, the dicing could beaccurately conducted without causing the shift or peeling of the wafer.After the irradiation with ultraviolet rays had been conducted under thesame conditions as those of the above test on adhesive force, the chipswere easily picked up by a needle in all of the Examples 12 to 20.

We claim:
 1. An actinic radiation-reactive pressure-sensitive adhesivecomposition having as essential components:a pressure-sensitive adhesivecompound comprising an acrylate copolymer, which is optionally mixedwith a cross linking agent, and an actinic radiation-curable resincomprising one or more polythiol compounds and one or more polyenecompounds, said polyene compounds each having at least two actinicradiation-reactive carbon-to-carbon double bonds from an acrylatecompound and the equivalent ratio of carbon-to-carbon double bonds tothe thiol groups being between 0.7:1.0 and 1.5:1.0, said compositionhaving a reduced adhesion strength after curing.
 2. An actinicradiation-reactive pressure-sensitive adhesive composition as set forthin claim 1, wherein the actinic radiation-curable resin is contained inthe adhesive composition in an amount of 1 to 500 parts by weight per100 parts by weight of the pressure-sensitive adhesive compound.
 3. Anactinic radiation-reactive pressure-sensitive adhesive composition asset forth in claim 1, wherein the actinic radiation-curable resin iscontained in the adhesive composition in an amount of 10 to 200 parts byweight per 100 parts by weight of the pressure-sensitive adhesivecompound.
 4. An actinic radiation-reactive pressure-sensitivecomposition as set forth in claim 1, having an adhesive force of from200 to 1000 g/20 mm for a semiconductor wafer before curing and anadhesive force of 100 g/20 mm or lower after curing.